Schizophrenia is the most common type of psychosis caused by excessive neurotransmission activity of the dopaminergic nervous system in the central nervous system. A number of drugs which block the neurotransmission of dopaminergic receptor in the central nervous system have been developed for use in treating schizophrenia. Among the drugs developed are phenothiazine-type compounds such as chlorpromazine, butyrophenone-type compounds such as haloperidol, and benzamide-type compounds such as sulpiride. These drugs improve so-called positive symptoms in the acute period of schizophrenia such as hallucinations, delusions, and excitations. Many drugs for treating schizophrenia, however, are not effective for improving the so-called negative symptoms which are observed in the chronic period of schizophrenia such as apathy, emotional depression, and hypopsychosis. The drugs currently used produce undesirable side effects such as akathisia, dystonia, Parkinsonism dyskinesia, and late dyskinesia, by blocking the neurotransmission of dopaminergic receptor in the striate body. Drugs that improve both the negative and positive symptoms of schizophrenia but diminish the undesirable side effect of schizophrenia are particularly desirable.
Aripiprazole is a pyschotropic drug that exhibits high affinity for dopamine D2 and D3, serotonin 5-HT1A and 5-HT2A receptors; moderate affinity for dopamine D4, serotonin 5-HT2C and 5-HT7, α1-adrenergic and histamine H1 receptors; and moderate affinity for the serotonin reuptake site. Aripiprazole has no appreciable affinity for cholinergic muscarinic receptors. The mechanism of action of aripiprazole, as with other drugs having efficacy in schizophrenia, is unknown. It has been proposed, however, that the efficacy of aripiprazole is mediated through a combination of partial agonist activity at D2 and 5-HT1A receptors and antagonist activity at 5-HT2A receptors.
U.S. Pat. No. 5,006,528 and Japanese Patent Kokai No. 02-191256 disclose that anhydride crystals of aripiprazole are typically manufactured by recrystallization of anhydride aripiprazole from ethanol or by heating aripiprazole hydrate at a temperature of 80° C.
The Proceedings of the 4th Japanese-Korean Symposium on Separation Technology (Oct. 6-8, 1996) disclosed that aripiprazole anhydride crystals may exist as Type-I and Type-II crystals. According to this reference, Type-I aripiprazole crystals can be prepared by recrystallizing aripiprazole from an ethanol solution or by heating aripiprazole hydrate at 80° C. Type-II aripiprazole crystals can be prepared by heating the Type-I crystals at 130° C. to 140° C. for 15 hours. This process is not easily applied to an industrial scale preparation of anhydride aripiprazole.
PCT publication WO 03/26659 discloses the preparation of anhydrous aripiprazole Type I and crystalline Forms A, B, C, D, E, F. and G. The powder x-ray diffraction spectrum for aripiprazole Form C has characteristic peaks at 12.6°, 13.7°, 15.4°, 18.1°, 19.0°, 20.6°, 23.5°, and 26.4° 2-theta. Typically, the process for preparing the crystalline forms comprises heating crystalline anhydrous aripiprazole. The process, however, is cumbersome because it requires crystalline anhydrous aripiprazole as the starting material. The process can include drying or heating the aripiprazole which may affect the distribution of crystalline forms and/or crystalline purity, if drying causes crystalline transformation from one crystalline form to another.
The methods of the invention provide procedures that consistently and reproducibly yield Form II consistently to increase the arsenal of crystalline forms available to the skilled artisan in preparing pharmaceutical formulations.